The onset of senescence or loss of replicative capacity in animal cells is a well established event in the life history of many cell types. As yet a genetic analysis of this event has proven cumbersome to perform due to the difficulty in obtaining stable variants of this phenotype. With the advent of cloning of entire genomes (shotgun cloning) a new avenue for genetic analysis can be approached. What is primarily required for such analysis is the methods for identifying those genes that are turned on or off during the onset of senescence. In this regard we have observed peptides that are produced in senescent human fibroblasts and not in their presencescent predecesors. We propose here to look at two general screening procedures designed to yield senescence-specific clones of human DNA. Any clones isolated by these procedures will be used to establish a correlation between the production of its product and the onset of senescence and to follow the metabolism of the mRNA for which it codes. With the procedures of DNA sequencing and transformation available a genetic analysis can be performed on senescence-specific genes.